It is well known to prepare telechelic polymers as shown by U.S. Pat. No. 4,276,394. Since this is a thermoplastic elastomer, it generally involves preparing diblock copolymers having a rubber segment and a plastic segment, at least one of which remains nonterminated and reactive. Although the above referred to U.S. Pat. No. 4,276,394 taught how to prepare these telechelic polymers, they were prepared by essentially a batch process and therefore the molecular weight of the resulting polymer was relatively wide and had molecules that had varying molecular weight and contained unfired and once-fired end groups.